Active Member

Ever since I got my Model 3, I've been wondering about the best way to take care of the battery for my particular driving habits - which is lots of super short trips and lots of access to chargers at home, work and various stores and restaurants. Is it best to plug it in all the time and keep it at 80% all the time, would it be better to let it drop to 40% full and then charge back up to 80% by not plugging it as much, etc.

I was browsing around last night reading articles about EV's and Tesla and found a discussion group that I hadn't seen before and then read a big post here about the lithium batteries in the Tesla Roadster but it seems to apply directly to the Model S/X/3 and everything in there matches my experiences with lithium-based batteries over the years.

These are the summary conclusions from the post - whenever you see "range mode", think "trip mode" on the Model 3 - or that range in the charging section that's greater than 80% highlighted as "trip".

Using range mode 100% a few times a year is fine, but if you are using hundreds of range mode charges it is going to cause premature battery aging. It is better to use Standard Mode (Roadster) or 80% or lower (Model S) charging and get a quick top up en route if you can.

It is better to use the lower end of Range Mode (low DOD) rather than the upper end if you must go further than Standard allows. However, if you run the battery down to the point it cannot calculate range, you are strongly advised to charge immediately.

Fast charging is fine because the packs are so large, the amount going into each cell is tolerable (a low “C” rate).

For longer periods off the road, store the car at a low DOD, then do a few full charges afterwards to rebalance the pack.

If your usage pattern is lots of shorter drives, it is better to keep the car near 50% charged instead of infrequent charging over the whole DOD range. If you have an OVMS, you can use its Advanced Charge Control features to do this automatically.

Before charging the Roadster after a long drive, cool the battery down by initiating a range mode charge. You can then switch back to Standard Mode after around an hour. If you have an OVMS, you can also use its Advanced Charge Control features to do this automatically.

I thought it was interesting, the author has lots of graphs and links to datasheets and everything written seems correct to me.

Now, granted this level of micromanaging might only add a bit more to the life of the battery and it's probably not necessary, but if you like dorking around with the charging interface like I do and you want to keep the battery longevity as healthy as possible, then my quick translation of the above text in Model 3 terms is:

If you are travelling and storing the car, store it at 50% charged by setting the max charge to 50% and leaving it plugged in.

Avoid charging to >80% as much as possible. Better to charge more often than use the whole range of the battery capacity.

For lots of short trips with constant access to a charger, try to keep it around 50-60% charged and only charge higher when you need to travel.

Living the Dream, Driving the Future!

@PatrickM I was looking for this EXACT type of Tesla charging recommendation being a low mileage (10-20 Miles Per Day / 9,000-ish Per Year) driver and a soon-to-be Model 3 owner.

The article I found found is pretty similar, if not a bit more basic, with a DAILY recommended limit of 70%. The source of the info is Jeff Dahn, a renowned battery researcher and the leader of Tesla’s research partnership through his battery-research group at Dalhousie University.

Active Member

70% sounds like a good limit and that makes sense to me. I've been charging to 75% - but I will drop it down to 70% instead since I agree that seems even better. And then if I'm going on a slightly longer trip, I'll take it up to 80% ahead of time but for nearly all of my driving I should be fine charging to 70% every day.

Active Member

when I had my delivery the rep stated that I should discharge fully once a month. Has anyone else read/seen this recommendation? If so, how exactly am I supposed to do this since I don't drive every day, and don't have a commute.

Dis Member

when I had my delivery the rep stated that I should discharge fully once a month. Has anyone else read/seen this recommendation? If so, how exactly am I supposed to do this since I don't drive every day, and don't have a commute.

Kick-Gas Contributor

when I had my delivery the rep stated that I should discharge fully once a month. Has anyone else read/seen this recommendation? If so, how exactly am I supposed to do this since I don't drive every day, and don't have a commute.

That is ABSOLUTELY bad advice that was recommended for NiCad batteries to cycle them periodically to avoid "memory" that can develop in NiCADs. Lithium is a completely different tech that doesn't require cycling.

For people that are trying to figure out their optimal charge habits, keep in mind that everyone's situation is different. Right now, all Model 3s have the long range battery but in the future, the short range battery will have a different optimal charge % for the same given daily commute distance. I believe that this is why the SR battery only has a 100k mi warranty whereas the LR battery has a 120k mi warranty. Statistically, the LR battery users will go through fewer charge cycles during the battery's lifetime for the same distance.

So the GENERAL formula people should be using would help keep the battery around 50% SOC but then depending on your situation, you may want to raise the target overnight charge % if you tend to have unexpected trips for errands. Keep in mind weekday charge % can be different from weekend charge % if your driving habits are different.

For example:
We will assume LR battery has 300mi at 100% and 150mi at 50%.
50 mi daily commute roundtrip. No typical planned errands.
This person can charge to 60% which would be roughly 180 mi range then will be at 130mi range when returning home. That should be plenty for extra errands that would arise and also keep SOC daily range from 45-60%. Each daily charge would only use 0.15 of a full charge cycle.

100 mi daily commute roundtrip.
This person can charge to 70% which would be roughly 210mi range then will be at 110mi range when returning home.
SOC daily range would be 35-70%. A daily charge would count as 0.35 of a full charge cycle.

Active Member

@PatrickM I was looking for this EXACT type of Tesla charging recommendation being a low mileage (10-20 Miles Per Day / 9,000-ish Per Year) driver and a soon-to-be Model 3 owner.

The article I found found is pretty similar, if not a bit more basic, with a DAILY recommended limit of 70%. The source of the info is Jeff Dahn, a renowned battery researcher and the leader of Tesla’s research partnership through his battery-research group at Dalhousie University.

Active Member

Is there any value to reducing the amperage for charging overnight? At the house it allows me to charge up to 36 amps, it typically only takes it 1-3 hours to reach my 70% limit. If I back off the amps to like 12, it still gets done long before I need it the next morning. Would that be better for the battery pack?

☰ > 3

Is there any value to reducing the amperage for charging overnight? At the house it allows me to charge up to 36 amps, it typically only takes it 1-3 hours to reach my 70% limit. If I back off the amps to like 12, it still gets done long before I need it the next morning. Would that be better for the battery pack?

the lower amps will potentially cause more loss between the electrical source and the battery, but don't think there is enough of a difference (from the on-board charger/battery perspective) between the 36A and 12A to make a long term difference.

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I really wish that Tesla would release a lot of hard data about battery life and charging levels so we're not so reliant on anecdotal evidence, but I strongly suspect that Tesla is treating that data as a competitive advantage.

Kick-Gas Contributor

I really wish that Tesla would release a lot of hard data about battery life and charging levels so we're not so reliant on anecdotal evidence, but I strongly suspect that Tesla is treating that data as a competitive advantage.

There are a few major characteristics about Tesla batteries that set them apart:

1 - unique chemistry of the lithium gel matrix and the anode/cathode materials
Tesla and Panasonic are truly at the head of the pack here and will soon have a cobalt-free chemistry which will dramatically drop the material costs of the battery pack.

2 - battery management software
Aside from the 8 year warranty on the cars, imagine the 10 year warranty on Powerwall2 which uses the same cells as the Model 3. I would dare say that the charge/discharge cycles on the home batteries are much more strenuous than those on the cars. Deeper discharges and more time spent at max charge (depending on settings).

3 - larger battery sizes
Many other EVs like Nissan/Toyota/BMW/Hyundai currently offer much smaller capacity batteries which not only limits range but dramatically shortens the lifespan of the battery. The lifespan of lithium batteries is not only a function of time but is typically measured in charge cycles. Current IEC standard stipulates that minimum capacity carried by a Lithium battery after 500 charging cycles should be 60%. This would be considered end of life at which time degradation occurs rapidly.

Hypothetically, if a Tesla lithium battery has a lifetime of 1000 charge cycles but you only charge 32% per day (about 100 miles on a LR Model 3 battery at 310 mi range), you are only using 0.32 charge cycle per day and have a rough battery lifespan of 3125 days which equals about 8.6 years and 312,500 miles). Assuming the same 100 mile per day charge on a SR Model 3 battery at 220 mi range would consume 0.45 charge cycles with a battery lifespan of 2222 days and 222,222 miles which is a little over 6 years.

Of course, most people don't drive 100 miles per day (36,000 miles per year) but you can see from these calculations why there is a shorter mileage warranty on the SR battery offered on the Model 3. Also, for people that think "I have a short commute and don't need to pay an extra $9k for the LR battery", you might reconsider the LR battery if you plan on keeping the vehicle for a longer time.

Top-Contributor

Is there any value to reducing the amperage for charging overnight? At the house it allows me to charge up to 36 amps, it typically only takes it 1-3 hours to reach my 70% limit. If I back off the amps to like 12, it still gets done long before I need it the next morning. Would that be better for the battery pack?

Seems I'm resurrecting an old thread here but one still relevant, perhaps more to winter charging. I recently switched from 120V/20A (which I've done for over a year) to a 240V/30A circuit. But for my daily commute, I really don't need the "fast" charging. I'm now up to 80% in around 1-3 hours. Then the battery sits there in the cold (single digits F not uncommon here). I'm thinking that I'm going to reduce the current when I charge so I spend most of the time overnight charging while plugged in. That avoids the battery cold soaks I've been getting. I can always dial up the charging juice when I need it. Any thoughts?

Dis Member

Seems I'm resurrecting an old thread here but one still relevant, perhaps more to winter charging. I recently switched from 120V/20A (which I've done for over a year) to a 240V/30A circuit. But for my daily commute, I really don't need the "fast" charging. I'm now up to 80% in around 1-3 hours. Then the battery sits there in the cold (single digits F not uncommon here). I'm thinking that I'm going to reduce the current when I charge so I spend most of the time overnight charging while plugged in. That avoids the battery cold soaks I've been getting. I can always dial up the charging juice when I need it. Any thoughts?

Note that research has shown that charging slowly is worse for battery degradation. You might want to consider a different tactic, such as charging to 70% right away, then adjust it up to 80% 30 minutes or an hour before leaving to help warm up the battery before departure.

That said, I doubt the effects are very noticeable, and I also bet that Tesla's battery chemistry isn't as susceptible to these effects, so going with your plan should be fine.

June 8, 2016
NSERC, Dalhousie University and Tesla Motors have established the
NSERC/Tesla Canada Industrial Research Chair that Jeff Dahn will hold
from June 8, 2016 to June 7, 2021. It is possible that the Chair will
be renewed in 2021. The goals of the Chair are to develop lithium ion
batteries with longer lifetime, higher energy density and lower cost.
As Dahn says, "Our goal is to do something useful, not publish papers
in Nature and similar journals"."

I'm trying to charge at about c/25; about 3 kw or 13 amps at 240 V. Don't know that it's optimal, but it seemed to be a point where the degradation was significantly less in Dahn's slides.

Slightly higher power, like 16 amps or about 3.8 kW would be better to overcome some losses in the system that basically waste power before it gets into the actual battery cells. And faster charging would have the benefit of further reducing exposure to the remaining parasitic side reactions, balanced against I^2R (and other) losses due to higher current.

Member

when I had my delivery the rep stated that I should discharge fully once a month. Has anyone else read/seen this recommendation? If so, how exactly am I supposed to do this since I don't drive every day, and don't have a commute.